Numerous scavenging systems not requiring a deflector-type piston have been tried: The pre-WW2 Villiers had exhaust ports on opposite sides of its cylinder and four transfer ports, in pairs, between them. A Barnes and Reinecke design had a ring of exhaust ports located above a ring of transfer ports and a part-conical piston crown, all of which sent the scavenging flow in a narrow column up the middle of the cylinder, and forced the exhaust outflow to follow a path down the cylinder walls. Curtiss employed multiple transfer and exhaust ports on opposite sides of a cylinder, and biased the direction of the transfers upward and to one side, so that the fresh charge spiraled up into the cylinder. But the best of the scavenging systems was one devised by a Dr. Schneurle, of Germany, in which a pair of mirror-image transfer ports flanked a single exhaust port, directing the scavenging flow toward the cylinder wall opposite the exhaust, and upward, to loop over and thus clear the cylinder. Schneurle's loop-scavenging method was patented by him, in 1925, and this had the effect of simultaneously elevating German industry's fortunes in the two-stroke engine field while forcing practically everyone else to seek alternative and less-efficient systems. Of course, now that the Schneurle patents have expired everyone employs some form of his scavenging method, although best results are being obtained with more than Schneurle's original pair of transfer ports.